"emerge -C foo" should remove all unmodified files from config protected directories. Currently portage leaves all old config files to /etc directory. This is serious problem when you update package and the new version installs config files to some other directory (f.e. apache-2.0.52-r2 to apache-2.0.52-r3 update). After update you have both old and new config files in /etc. Reproducible: Always Steps to Reproduce:
there's already a bug filed about this i just cant remember the #/summary off the top of my head
*** This bug has been marked as a duplicate of 8423 ***